Potentiometer for motorized mirror

ABSTRACT

A position sensing device for a mirror assembly displaced by an electric motor for a mirror assembly having a memory unit which relies upon position information. The position sensing device connects directly between the housing reinforcement member and the mirror glass. The position sensing device also includes inherent damping capabilities. A dampening assembly provides additional damping capabilities, thereby further limiting vibration of the mirror due to road and wind vibration.

This is a continuation-in-part of U.S. patent application Ser. No.09/352,088, filed Jul. 14, 1999, now U.S. Pat. No. 6,254,242.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to vehicle mirror systems which may beadjusted by electrically controlled motors and, more particularly, to apotentiometer for measuring the position of the mirror glass whichincludes dampening properties to minimize vibrations affecting themirror glass.

2. Discussion

In order to facilitate use of exterior mirror assemblies on vehicles,many mirror assemblies come equipped with a pair of electrical motorswhich may be operated within the vehicle. Electrical signals sent to themotors by an internal vehicle switch causes displacement of the motorswhich in turn causes displacement of the mirror glass. This facilitatesadjusting the position of the mirror glass so that driver can obtain anoptimum view with minimum effort. To further facilitate the use ofmotorized mirror assemblies for operation by the driver, some motorizedmirror assemblies include a memory so that vehicle mirror or mirrors canbe set to a predetermined position and the position can be memorized.The mirror or mirrors can later be automatically returned to thepredetermined position for a particular vehicle operator. One or morevehicle operators can be accommodated by providing corresponding memorysettings for each driver.

Mirror assembly systems having memory capabilities include one or a pairof motors to displace the mirror glass about a pivot point for themirror glass. The motors typically include a position sensor whichmeasures displacement of the motor to determine the position of themirror glass. In such systems, the position sensor attaches to the motorhousing at one end and to the gear train at the other end in order tomeasure displacement of the gear train. By arranging the position sensorin this manner, the position sensor will have inherent inaccuracies dueto the play or slop in the gear train, commonly known as backlash. Suchsystems effectively measure the position of the motor, rather than theposition of the mirror glass.

Existing systems utilize a position sensor which has no dampingcapability. Because exterior mirrors are subject to road vibrationtransmitted through the vehicle and wind vibration, such positionsensing devices output a signal adversely affected by the vibrationexperienced by the mirror glass. The varying signal introduces inherentinaccuracy when attempting to position the mirror when the vehicle is inoperation. Although the position signal output by the position sensorcan be filtered, this adds to the cost of the electrical control systemfor the mirror assembly.

It is an object of the present invention to provide a mirror assemblyhaving a position sensor which measures the actual position of themirror glass.

It is a further object of the present invention to provide a mirrorassembly having a position sensor for the mirror glass which is detachedfrom the motor mechanism.

It is yet a further object of the present invention to provide aposition sensor for the mirror glass which is unaffected by backlash inthe motorized gear train.

It is yet a further object of the present invention to provide aposition sensor having dampening properties to compensate for noise andvibration experienced by the mirror assembly.

SUMMARY OF THE INVENTION

The invention is directed to a mirror assembly for a vehicle. The mirrorassembly includes a mirror housing and a reflective element. A backingassembly supports the reflective element and includes a pivot pointabout which the backing assembly and the reflective element pivot. Anelectric motor is mounted to the mirror housing and is responsive to anelectrical input to displace the backing assembly and supportedreflective element about the pivot point. A position sensor detectsdisplacement of the backing assembly, and the position sensor includes adampener to dampen movement of the position sensor.

These and other advantages and features of the present invention willbecome readily apparent from the following detailed description, claimsand drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings, which form an integral part of the specification, are tobe read in conjunction therewith, and like reference numerals areemployed to designate identical components in the various views:

FIG. 1 is a front perspective view of the mirror assembly mounted to avehicle arranged in accordance with the principles of the presentinvention;

FIG. 2 is a rear perspective view of the mirror assembly of FIG. 1;

FIG. 3 is a horizontal cross-section of the mirror assembly showing theposition sensor arranged in accordance with the principles of thepresent invention;

FIG. 4 is an exploded view of the position sensor assembly;

FIG. 5 is a top view of the combined sensor and dampener element;

FIG. 6 is a side cross-sectional view of the combined dampener andposition sensor along Section 5—5 of FIG. 5;

FIG. 6a perspective view showing the friction spring and wiping members;

FIG. 7 is a further side cross-sectional view of the combined dampenerand position sensor along Section 7—7 of FIG. 5;

FIG. 8 is a sectional view of an alternate embodiment of a combinedsensor and dampener element; and

FIG. 9 is a second cross-sectional view of the combined sensor anddampener element of FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described with respect to FIGS. 1-4.Mirror assembly 10 attaches to a vehicle 12 in proximity to the A-pillar14. In the embodiment shown, mirror assembly 10 is a left side mirrorassembly, as would be used for a driver side and rear view exteriormirror. Mirror assembly 10 attaches to the front portion of a vehicledoor 16 or to A-pillar 14 via a bracket 18. Bracket 18 attaches tohousing 20. Preferably, housing 20 pivots with respect to bracket 18 sothat housing 20 may be displaced in response to an applied force inorder to prevent housing 20 from breaking off from bracket 18.

Mirror glass 22 is supported within housing 20. Housing 20 includes ahousing reinforcement member 24 which is mounted to bosses or supports26. Bosses or supports 26 may be integrally formed with housing 20, suchas through an injection molding process, or may be attached to housing20 through a separate process. Housing reinforcement member 24 fastensto bosses 26 using a threaded fastener, rivet, heat staking process, orother suitable fasteners. Housing reinforcement member 24 supports abacking plate 28 which attaches to and supports mirror glass 22. Backingplate 28 preferably pivots with respect to housing reinforcement member24 about a center point 30.

Pivotal movement of backing plate 28 and attached mirror glass 22 isaccomplished through electronic adjustment means. In particular, a motor32 such as a direct current (DC) operated motor includes a shaft 34which moves in an axial direction upon actuation of motor 32. Shaft 34includes a head 36 which connects to backing plate 28. Displacement ofmotor 32 causes backing plate 28 and mirror glass 22 to rotate aboutcenter point 30. In the sectional view of FIG. 3, this displacementoccurs about a vertical axis in proximity to center point 30, therebyvarying the distance away from the vehicle which the operator may viewthrough mirror glass 22.

Opposite center point 30 of motor 32, a position sensor assembly 38 ismounted to housing reinforcement number 28. Position sensor assembly 38will be described herein as a dampened potentiometer which has a varyingresistance in accordance of displacement of a wiper or shaft. Positionsensor assembly 38 includes a potentiometer 40. Potentiometer 40includes a wiper or shaft 42. Shaft 42 may be displaced into and out ofpotentiometer housing 44. The opposite end of shaft 42 includes a head46. Potentiometer 40 includes a trio of electrical leads 48 and operatesas is well known in the art. Briefly, displacement of wiper or shaft 42into and out of potentiometer housing 44 varies the resistance between apredetermined pair of electrical leads 48. By determining the variationin resistance in accordance with displacement and storing the same inmemory or generating a function correlating the tow, displacement ofshaft 42 can be determined in accordance with vibration across the twopredetermined two electrical leads 48.

In a preferred embodiment, potentiometer housing 44 includes a viscousfluid which dampens movement of shaft 42 into and out of potentiometerhousing 44, thereby dampening vibrational-type movement of mirror glass22. In order to maintain a seal of potentiometer housing 40, an o-ring50 is disposed around shaft 42 passes into potentiometer housing 44.

In addition to the dampening properties described above, mirror assembly10 is also shown with a dampening assembly 52. Dampening assembly 52connects to housing reinforcement member 24 at one end and to backingplate 28 at another end. Dampening assembly 52 includes a friction pin54 having a head 56 and a shank 58. Friction pin 54 includes flange 60arranged between head 56 and shank 58. Flange 60 includes a socket 62which receives head 46 of potentiometer 40. Engagement between frictionpin 54 and potentiometer 40 enables friction pin 54 to dampen movementof potentiometer 40. The shank 58 of friction pin 54 passes through adampening spring 64 which exerts a clamping force upon shank 58 tothereby dampen movement of friction pin 54. A pair of symmetricretaining lips 66 hold dampening spring in position to housingreinforcement number 24. Retaining spring 64 constricts movement offriction pin 54 to induce drag on the pin as it moves in and out.

As shown in FIG. 4, one of the retaining lips 66 is formed integral withpotentiometer case 68. Potentiometer case 68 may be formed integral withhousing reinforcement member 24 or may be mounted independently tohousing reinforcement member 24. Potentiometer case 68 receivespotentiometer 40 and has a pair of protrusions 70 which engage dimplesformed in potentiometer housing 44. Mounting of potentiometer housing 44within potentiometer case 68 as described herein enables potentiometer42 to rotate about the interconnection between protrusions 70 anddimples 72. This compensates for slight arcuate movement of friction pinhead 56.

In operation, potentiometer case 68, retaining lips 66, and dampeningspring 64 are attached to housing reinforcement member 24.Alternatively, retaining lips 66 and potentiometer case 68 may be formedintegral with housing reinforcement member 24, and dampening spring 64may be installed thereafter. Friction pin head 56 attaches to backingplate 28 at a socket 74 and translates with displacement of backingplate 28 and attached mirror glass 22. As backing plate 28 and mirrorglass 22 experience vibration transmitted through the vehicle and fromwind, the interaction between shank 58 and dampening spring 64 dampensaxial movement of friction pin 54, thereby dampening axial movement ofwiper or shaft 42 of potentiometer 40. As described above, adjustment ofbacking plate 28 and mirror glass 22 by motor 32 causes slight arcuatemovement of head 56 and shank 58 about dampening spring 64, therebycausing corresponding arcuate movement of head 46 and shaft 42 ofpotentiometer 40. This slight tendency for arcuate movement ofpotentiometer 40 is compensated by enabling rotation of potentiometer 30about the interconnection between protrusions 70 and dimples 72.

In view of the foregoing, one can see that the subject inventionprovides an improved position sensing assembly for a motorized mirror.In particular, direct attachment between the position sensor assemblyand the backing plate provides more accurate positional information, asit eliminates inaccuracies introduced by gear backlash. Further, theposition sensor is located opposite the pivot point about which thebacking plate pivots when displaced by the electric motor. Further yet,a dampening device may be included integral to the potentiometer or anadditional dampening device may provide more stability to the mirrorglass and a more stable output signal from the position sensor assembly.Further yet, the position sensor assembly is embodied as a free standingassembly which may be retrofit onto existing systems and may beseparated from the motorized unit.

Referring now to FIGS. 5-7, FIG. 5 depicts a plan view of the top of acombined dampener and position sensor 140 showing the four sided outlineof the recess within which the carrier shaft moves longitudinally inthis depiction in and out of the page.

The carrier shaft 142 is shown in more detail in FIGS. 6 and 7, whichshow two cross-sections of the combined dampener and position sensor140. FIG. 6 depicts a section 5—5 of FIG. 5, showing, in side profile,the recess housing 144 and attached to the base of carrier shaft 142 isa two pronged friction spring 146. The U-shaped spring is attached tothe base of the carrier shaft 142 by the press fit of an aperture in thebase of the spring over a slightly oversized pin so as to becomefrictionally engaged with the end of the carrier shaft. The twosubstantially planar spring portions 143 and 143 a are biased againstopposed inner walls of the cavity 144 a of the housing 144. This ismerely a preferable arrangement since there may be other arrangements ofsprings such as for example two or more surfaces of the sides of thespring arranged to be slidably biased against the inner walls of thecavity.

The use of a U-shaped spring is merely preferable since many otherarrangements of springs, resilient surfaces and friction applyingelements could be provided on the movable carrier shaft 142.

A preferred position sensing arrangement is depicted in side profile inFIG. 7, comprising an outwardly biased wiper contact element 148 ofconductive material which is attached to the base of the longitudinallymovable carrier shaft 142 and arranged to wipingly contact the surfaceof a resistive track or tracks 149 located on a printed circuit board 49a positioned along a wall of the recess 144 a. There are in FIGS. 5-7,three wires 150, 152 and 154 connecting the position sensor printedcircuit board with remote electronics used to interpret the signalprovided by the position sensor arrangement.

An additional dampening and position sensor located in recess 120 wouldprovide additional dampening as well as a position sensing means formeasuring the relative position of the mirror with respect to the mirrorhousing along at least the axis controlled by discrete drive assembly124.

The top of the carrier shaft 142 has a bulbous shaped end 156 which isshaped to provide a pivotal engagement with the rear of the rear viewmirror. The carrier shaft 142 moves longitudinally in and out of therecess 144 as a result of the motor controlled movement of the mirror.As the discrete drive assembly 122 moves the mirror away from the mirrorhousing, the mirror pivots about ball joint pivot 138 and the carriershaft reciprocally moves inwards of the cavity 144 a, resisted by thefriction applied on the opposed inner walls of the recess 144 a byspring 146 and at the same time the wiper contact 148 slides across theresistive tracks 149 and provides a means to interpret the relativeposition of the mirror (in that particular axis) with respect to themirror housing. Electrical contacts generally shown at 150 provideelectrical connection for securing the position of the potentiometer anddampener.

When two dampener and position sensors are used, any position of themirror can be detected and hence any mirror position can be replicatedby moving the mirror until the same relative signals from the positionsensors are achieved.

Clearly it is advantageous to keep the wiper contact clean so as toprovide consistent electrical conductivity and thus repeatable positionsensing as well as maintaining substantially constant frictioncharacteristics so that the electric motors will be able to providesufficient motive force to overcome that resistance. Thus, the apertureabout the carrier shaft at the opening of the recess 144 a is preferablysealed against the ingress of dust and particulate matter as well asmoisture all of which could adversely effect the conductivecharacteristics of the position sensor and the friction characteristicsof the dampener. A sealing grommet 158 is provided which preferably notonly seals the aperture about the carrier shaft, but also covers theterminals of the electric wiring 150, 152 and 154 entry point to theassembly.

Furthermore, the combined dampener and position sensor is manufacturedso that it can be engaged with both the rear of the rear view mirror andthe mirror housing in a typically pre-existing recess. FIG. 6 depictscooperating tabs 160 and grooves 162 which allow the combined dampenerand position sensor to snap into place. This allows for the retrofittingof the dampener and position sensor into mirror assemblies which maypreviously have only housed a dampener.

Referring now to FIGS. 8 and 9, there is shown a combined dampener andposition sensor 240. In this embodiment, an outer housing 244 includes acavity 244 a. In the embodiment of the combined dampener and positionsensor 240 shown in FIGS. 8 and 9, the dampening method is differentthan that shown in FIGS. 5-7. The friction member 246 includes a pair offlexible legs 248 and 250 which are pressed against the sidewall cavity244 a by way of a compressed spring 252. The shaft includes a thinned,bendable web 254 for controlled bending of the shaft portionfacilitating controlled friction of the friction member 248.Additionally, friction member 248 includes raised protrusions 256 and258 which also facilitate the controlled friction motion of the frictionmember 246. A printed circuit board 260 is provided and cooperates withthe wiper contact 262 to provide the positional inputs of thepotentiometer. A cap member 264 seals the unit and a boot generallyshown at 266 seals the cavity 244 a. The cap member 264 also includeselectrical contacts for the printed circuit board.

While specific embodiments have been shown and described in detail toillustrate the principles of the present invention, it will beunderstood that the invention may be embodied otherwise withoutdeparting from such principles. For example, one skilled in the art willreadily recognize from such discussion and from the accompanyingdrawings and claims that various changes, modifications and variationscan be made therein without departing from the spirit and scope of theinvention as described in the following claims.

What is claimed is:
 1. A mirror assembly for a vehicle comprising: amirror housing; a reflective element; a backing assembly supported bythe mirror housing, the backing assembly supporting the reflectiveelement, the backing assembly having a pivot point about which thebacking assembly and the reflective element pivot; an electric motormounted to the mirror housing, the electric motor being responsive to anelectrical input to displace the backing assembly and supportedreflective element about the pivot point; a combination positioningsensor and dampener assembly operatively connected to the backingassembly and the mirror housing, the combination position sensor anddampener assembly dampening movement of the backing assembly andgenerating an output signal in accordance with displacement of thebacking assembly with respect to the mirror housing.
 2. The mirrorassembly of claim 1 wherein said combined position sensor and dampenerassembly comprises a dampener housing, including an elongated cavity, arod portion with a friction end portion is slidably associated in saidcentral cavity, a potentiometer board containing resistive tracks, and awiper operably associated in said cavity therewith for reading therelative position of the wiper along the board.
 3. The mirror assemblyof claim 2 wherein said friction end portion includes a spring loadedportion for engaging the sides of said aperture.
 4. The mirror assemblyof claim 3 wherein said spring loaded portion includes a leaf typespring which engages the side of said aperture.
 5. The mirror assemblyof claim 3 wherein said spring loaded portion includes a pair of opposedfriction members with a coil spring therebetween for urging the opposedfriction members against opposed walls of said aperture.
 6. The mirrorassembly of claim 5 wherein said rod includes a reduced thicknessportion for providing flexibility to said shaft.
 7. The mirror assemblyof claim 6 wherein bearing protrusions are formed or said frictionmember for facilitating off axis movement between said rod and saidfriction member.